OpenCL error when GPU rendering in Cycles
had exactly the same problem when I was trying to view (not even render) a scene with volumetrics in it.
My scene had: a sky environment texture and a default cube with principle volume shader puggled into volume output. Here's what worked for me:-

In anything but render view, switch to render with CPU.
Go into render view
Then in render view swithc to render with GPU.

I have no idea why this worked for me or if it will do you or anyone else any good. All I can say is I think the problem is with OpenCL, kinda wish I'd brought an Nvidia GPU now.